US 10,706,782 B2Granted

TFT pixel threshold voltage compensation circuit with short one horizontal time

AssigneeSharp Kabushiki Kaisha

InventorsTong Lu, Michael James Brownlow

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Abstract

A pixel circuit includes a drive transistor that controls an amount of current to a light-emitting device, and a second transistor connected to the gate of the drive transistor and a second terminal of the drive transistor, such that when the second transistor is in an on state the drive transistor becomes diode-connected. A threshold voltage of the drive transistor is compensated during a compensation phase while the drive transistor is diode connected. The light-emitting device is connected between the drive transistor and at a second node to a first voltage input. The pixel circuit further includes a storage capacitor having a first plate connected to the gate of the drive transistor, and a programming capacitor having a first plate connected to a second plate of the storage capacitor, and a second plate of the programming capacitor is electrically connected to a data voltage input during a data programming phase. The second plate of the storage capacitor and the first plate of the programming capacitor are connectable to a reference voltage to perform the compensation phase independently of the programming phase, and the storage capacitor and the programming capacitor are series connected during the emission phase.

Claims20

Dependent claims

A pixel circuit for a display device operable in a compensation phase, a data programming phase, and an emission phase, the pixel circuit comprising:

a drive transistor configured to control an amount of current to a light-emitting device during the emission phase depending upon a voltage applied to a gate of the drive transistor;
a second transistor connected to the gate of the drive transistor and a second terminal of the drive transistor, such that when the second transistor is in an on state the drive transistor becomes diode-connected such that the gate and the second terminal of the drive transistor are electrically connected through the second transistor, wherein a threshold voltage of the drive transistor is compensated during the compensation phase while the drive transistor is diode connected;
wherein the light-emitting device is electrically connected at a first node to the second terminal of the drive transistor during the emission phase, and is connected at a second node to a first voltage input;
a storage capacitor having a first plate directly connected to the gate of the drive transistor, and
a programming capacitor having a first plate directly connected to a second plate of the storage capacitor at a common node connection, and a second plate of the programming capacitor is electrically connected to a data voltage input during the data programming phase;
wherein the common node connection of the second plate of the storage capacitor and the first plate of the programming capacitor is electrically connectable to a reference voltage input to perform the compensation phase independently of the programming phase, and the storage capacitor and the programming capacitor are series connected to the gate of the drive transistor during the emission phase.

3 more elements

A method of operating a pixel circuit for a display device comprising the steps of:

providing a pixel circuit comprising:
a drive transistor configured to control an amount of current to a light-emitting device depending upon a voltage applied to a gate of the drive transistor;
a second transistor connected to the gate of the drive transistor and a second terminal of the drive transistor, such that when the second transistor is in an on state the drive transistor becomes diode-connected such that the gate and the second terminal of the drive transistor are electrically connected through the second transistor;
a storage capacitor having a first plate directly connected to the gate of the drive transistor, and
a programming capacitor having a first plate directly connected to a second plate of the storage capacitor at a common node connection, and a second plate of the programming capacitor is electrically connectable to a data voltage input;
performing a compensation phase to compensate a threshold voltage of the drive transistor comprising diode-connecting the drive transistor through the second transistor and applying the reference voltage at the common node connection of the second plate of the storage capacitor and the first plate of the programming capacitor, thereby electrically isolating the programming capacitor from the storage capacitor;
performing a data programming phase to program the data voltage to the programming capacitor comprising applying the data voltage at a second plate of the programming capacitor;
and
performing an emission phase during which light is emitted from the light-emitting device comprising applying the reference voltage at the second terminal of the programming capacitor, wherein the storage capacitor and the programming capacitor are series-connected to the gate of the drive transistor, and applying a driving voltage through the drive transistor to the light emitting device.

6 more elements

Dependencies are inferred from the claim text.

Facts

Application: 16/171,718Filed 26 Oct 2018
Published: US 2020/0135105 A130 Apr 2020
Granted: 7 Jul 2020
Term ends: Not estimatedThe source records don’t support an estimate.

Classification10 codes

G09G 3/3258
Using an active matrix: with pixel circuitry controlling the voltage across the light-emitting element
G09G 3/3233
Using an active matrix: with pixel circuitry controlling the current through the light-emitting element
H10D 86/40
Integrated devices formed in or on insulating or conducting substrates, e.g. formed in silicon-on-insulator [SOI] substrates or on stainless…
H10D 86/60
Characterised by multiple TFTs: wherein the TFTs are in active matrices